Biotreatment　of　high　load　hydrogen　sulfide　(H2S)　can　lead　to　rapid　acidification　of　a　bioreactor,　which　greatly　challenges　the　application　of　bio-desulfurization　technology.　In　this　study,　the　bio-desulfurization　performance　was　improved　by　enriching　acidophilic　mixotrophic　sulfur-oxidizing　bacteria　(SOB)　by　adding　organics　under　extremely　acidic　conditions　(pH　＜　1.0).　A　biotrickling　filter　(BTF)　for　the　removal　of　H2S　was　established　and　operated　under　pH　＜　1.0　for　420　days.　In　the　autotrophic　period,　the　maximum　H2S　elimination　capacity　(ECmax-H2S)　was　135.8　g/　m(3)/h　with　biofilm　mass　remaining　within　11.1　g/L-BTF.　The　autotrophic　SOB　bacterium　Acidithiobacillus　was　dominant　(62.1　%).　When　glucose　was　added　to　the　BTF　system,　ECmax-H2S　increased　by　272　%　to　464.3　g/m(3)/h　as　biofilm　mass　increased　to　22.3　g/L-BTF.　The　acidophilic　mixotrophic　SOB　bacteria　Mycobacterium　(78.4　%)　and　Alicyclobacillus　(20.7　%)　were　enriched　while　Acidithiobacillus　was　gradually　eliminated　(＜　0.1　%).　Furthermore,　the　major　sulfur　me-tabolism　pathways　were　identified　to　explore　the　desulfurization　mechanism　under　extremely　acidic　conditions.　To　maintain　optimal　desulfurization　performance　and　avoid　biofilm　overgrowth　in　the　BTF　system,　biofilm　mass　should　be　maintained　within　20-22　g/L-BTF.　This　can　be　achieved　by　adding　1.0　g/L-BTF　glucose　every　20　days　under　a　load　rate　of　H2S　in　50-90　g/m3/h　anda　trickling　liquid　velocity　of　1.8　m/h.　Extremely　acidic　conditions　eliminated　non-aciduric　microorganisms　so　that　the　addition　of　organics　can　increase　the　abundance　of　acidophilic　mixotrophic　SOB　(＞　99　%),　thus　offering　a　novel　strategy　for　enhancing　H2S　removal.